• 한국식품과학회지
• /
• 제39권5호
• /
• pp.506-514
• /
• 2007

비열 살균 기술인 high voltage PEF를 이용하여 당근 주스를 처리하였을 때 당근주스의 살균력과 저장 중 품질 변화를 관찰하였다. 전기장의 세기를 50, 60, 70kV/cm에서 처리 시간을 달리하여 당근주스를 처리한 결과 전기장의 세기가 증가함에 따라 일반 세균과 효모 및 곰팡이 모두 감소하였다. 효모 및 곰팡이는 65 kV/cm, $200{\mu}s$ 처리시 모든 균이 사멸되었고 일반세균은 멸균에까지 이르지는 못하였으나 70 kV/cm $200{\mu}s$ 처리 후 4 log cycle 정도 감소되었다. 고전압 펄스 전기장 처리에 사용되는 펄스 파형인 square wave pulse와 exponential decay pulse가 살균효과에 미치는 차이를 비교하기 위하여 각각 4.25와 6.25의 pH에서 PEF 처리를 하여 실험하였다. 그 결과 square wave pulse를 이용한 PEF의 살균효과가 exponential decay pulse를 이용하였을 때보다 우수하였으며 처리 시간이 길어질수록, 당근주스의 pH가 낮을수록 두 파형 사이의 살균효과는 더 큰 차이를 나타내었다. 온도 및 pH의 병합처리가 PEF의 살균효과에 미치는 영향을 알아보기 위하여 온도 및 pH를 달리하여 55kV/cm, $132{\mu}s$의 조건에서 PEF 처리한 결과 병합 처리시 살균효과가 눈에 띄게 증가하는 것을 관찰할 수 있었다. PEF 처리한 당근주스의 저장 시 품질변화를 관찰한 결과 pH 와 열처리를 PEF와 병합하여 처리한 후 $4^{\circ}C$ 저장한 당근 주스에서만 pH, $^{\circ}Brix$, 산도, 색도 그리고 ${\alpha}-,\;{\beta}-carotenes$함량에 눈에 띄는 차이를 나타나지 않았으며, 28일 동안 균의 생육을 관찰할 수 없었다.

• Journal of information and communication convergence engineering
• /
• 제19권4호
• /
• pp.269-275
• /
• 2021

Light-emitting diodes (LEDs) are modulated using a square wave pulse sequence for flicker prevention and dimming control in visible light communication (VLC). In a VLC transmitter, the high and low bits of the non-return-to-zero (NRZ) data are converted to two square waves of different frequencies, which continue for a finite time defined by the fill ratio in an NRZ bit time. As the average optical power was kept constant and independent of data transmission, the LED was flicker-free. Dimming control is carried out by changing the fill ratio of the square wave in the NRZ bit time. In the experiments, the illumination of the LED light was controlled in the range of approximately 19.2% to 96.2% of the continuous square wave modulated LED light. In the VLC receiver, a high-pass filter combined with a latch circuit was used to recover the transmitted signal while preventing noise interference from adjacent lighting lamps.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
• /
• pp.184-187
• /
• 1990

This paper presents the self-matched line pulse generator and the concerned principles on its operation and characteristics are mentioned. The circuit consists of a charged transmission line and a high speed switch, and it generates a square wave pulse with the very fast rise time. The generated waveform depends on the load resistance. As the load resistance is infinite, a single rectangular wave pulse is generated and its efficiency is nearly unity.

• 대한전자공학회논문지
• /
• 제26권11호
• /
• pp.1819-1828
• /
• 1989

In this paper, we determined the modulation index for minimization of speed ripple and position error using maximum speed ripple (SRF) and maximum position error(PEF) in current source TPWM inverter. Through computer simulation, we compared with total current harmonic distortion, SRF and PEF for square wave modulation method and TPWM method. As a result, it turns out that square wave modulation method is superior to TPWM method of 3 pulses per half cycle in speed ripple and position error contents. And TPWM is better than square wave method when pulse number is more than 5. Also, in these pulse numbers, moduladtion index of minimum speed ripple and munimum position error is 0.91.

• 디지털산업정보학회논문지
• /
• 제12권4호
• /
• pp.25-31
• /
• 2016

In this research, to analyze the concentration of heavy metal ions in water, we tried to find the measuring time at which the faradaic electric currents flowing by the pure oxidation-reduction reaction from the pushing up mercury electrode of the stripping scan square wave voltammetry(SV+SWV) methods system becomes larger than the capacitance electric current. In order to do this, a method for analyzing signals using FPGA has been designed and we conducted 120 experiments using it. As a result, when the frequency of the square wave is 40Hz, The valid potential-current signal was measured from 96.6667% to 96.7155% of the end of the pulse of the forward and reverse, and the optimal signal was measured at 96.6667%. In addition, the experiment was carried out 40 times by changing the pulse height of the square wave from 10Mv to 40Mv. As a result, at a size smaller than 40Mv, there is little change in the magnitude of the potential-current, and an invalid signal was generated when it is out of this size.

• 한국전기전자재료학회논문지
• /
• 제26권6호
• /
• pp.472-477
• /
• 2013

This paper carried out the comparative analysis on ground impedance of a carbon block and a copper rod. Two types of grounding electrode were compared ; a carbon block (L : 1 m, ${\Phi}$ : 245 mm) buried at a depth of 0.8 m and a three-linked copper rod (L : 1 m, ${\Phi}$ : 10 mm) of equilateral triangles with 1 m spacing. Ground impedance depending on applied current source was evaluated by the application of a sine wave current with 60 Hz ~ 3.5 MHz, a fast-rise pulse with rising time of 200 ns, a standard lightning impulse of $8/20{\mu}s$ and a 600 Hz square wave. Ground impedance for both electrodes were almost the same value below 100 kHz, and increased rapidly afterwards. The maximum ground impedance appeared $400{\Omega}$ at around 1.5 MHz. Ground impedance of the carbon block was lower at the square wave and was higher at fast-rise pulse than that of the copper rod. Also, ground impedance as ages showed no difference for the last 8 months. From the results, it is likely that ground performance for both electrodes shows no difference against commercial frequency and lightning impulse current, while the copper rod shows better performance against a fast-rise pulse with rise-time of a few hundred ns.

• Food Science and Biotechnology
• /
• 제16권6호
• /
• pp.1082-1084
• /
• 2007

Ultra-high temperature (UHT) processed full fat milk inoculated with Escherichia coli, Pseudomonas fluorescens, and Bacillus stearothermophilus was exposed to 30-60 kV/cm square wave pulsed electric field (PEF) with $1\;{\mu}sec$ pulse width, and $26-210\;{\mu}sec$ treatment time in a continuous PEF treatment system. Eight log reduction was obtained for E. coli and P. fluorescens and 3 logs reduced for B. stearothermophilus under PEF treatment conditions of $210\;{\mu}sec$ treatment time, 60 kV/cm pulse intensity at $50^{\circ}$. There was no significant change in pH and titration acidity of milk after PEF treatment. The electrical energy required to achieve 8 log reduction for E. coli and P. fluorescens was estimated to be about 0.74 kJ/L.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2004년도 ICCAS
• /
• pp.682-685
• /
• 2004

This paper investigated a method for classifying emotional states by using pulse wave signal. It focused on finding effective features for emotional state classification. The emptional states considered here consisted of interest and neutral. Classification experiments utilized 65 and 60 samples of interest and neutral states respectively. We have investigated 19 features derived from pulse wave signals by using both time domain and frequency domain analysis methods with 2 classifiers of minimum distance (normalized Euclidean distanece) and ${\kappa}$-Nearest Neighbour. The Leave-one-out cross validation was used as an evaluation mehtod. Based on experimental results, the most efficient features were a combination of 4 features consisting of (i) the mean of the first differences of the smoothed pulse rate time series signal, (ii) the mean of absolute values of the second differences of thel normalized interbeat intervals, (iii) the root mean square successive difference, and (iv) the power in high frequency range in normalized unit, which provided 80.8% average accuracy with ${\kappa}$-Nearest Neighbour classifier.

• Journal of Plant Biology
• /
• 제29권1호
• /
• pp.1-10
• /
• 1986

Intra- and inter-specific protoplast fusion of tobacco (Nicotiana tabacum cv. Virginia 115) and pea (Pisum sativum cv. Sparkle) were carried out in highly inhomogeneous alternating electric fields. Under the electric field of alternating current (AC, sine wave), 600 V/cm and 800 kHz for tobacco protoplast, and 600 V/cm and 700 kHz for pea protoplasts, the protoplasts were aggregated in pearl chains. Intra-specific protoplast fusions were most effectively induced within the aggregates of tobacco and pea, respectively, by the additional application of a single high field pulse of direct current (DC, square wave) at 1 kV/cm for 50 $mutextrm{s}$. Inter-specific fusions between protoplasts of the two plants were most effectively induced in the electric field of 600 V/cm and 700 kHz, and square wave pulse at 1 kV/cm for 50 $mutextrm{s}$. The duration of the pulse over the electrical breakdown voltages was simulated from 1 to 100 $mutextrm{s}$ in both tobacco and pea protoplast. The yield of the electrofusion products was significantly high (above 60%), compared with that (20%) of the standard fusion method by polyethylene glycol (PEG) 4,000, and the viability of electrofused protoplasts was above 70%, but that of PEG-fused protoplasts 8~16%, when determined by Evan's blue staining method.

• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1515-1527
• /
• 2018

This paper presents a sensorless speed control of IPMSM (Interior Permanent Magnet Synchronous Motor) using the high-frequency (HF) square wave injection method. In the proposed HF pulsating square wave injection method, injection voltage is applied into the estimated d-axis of rotor and high-frequency induced q-axis current is considered to estimate the rotor position. Conventional square wave injection methods may need complex demodulation process to find rotor position, while in the proposed method, an easy demodulation process based on the rising-falling edge of the injected voltage and carrier induced q-axis current is implemented, which needs less processing time and improves control bandwidth. Unlike some saliency-based sensorless methods, the proposed method uses maximum torque per ampere (MTPA) strategy, instead of zero d-axis command current strategy, to improve control performance. Furthermore, this paper directly uses resultant d-axis current to detect the magnet polarity and eliminates the need to add an extra pulse injection for magnet polarity detection. As experimental results show, the proposed method can quickly find initial rotor position and MTPA strategy helps to improve the control performance. The effectiveness of the proposed method and all theoretical concepts are verified by mathematical equations, simulation, and experimental tests.